Crimped textile products



June 12, 1962 A. L. BREEN 3,038,236

CRIMPED TEXTILE PRODUCTS Filed NOV. 3, 1958 FlG.l

2 Sheets-Sheet 1 INVENTOR ALVIN L. BREEN BY W $47 ATTORNEY June 12, 1962 Filed Nov. 3, 1958 A. L. BREEN CRIMPED TEXTILE PRODUCTS 2 Sheets-Sheet 2 INVENTOR 54 ALVIN L. BREEN U ite ice 3,638,236 CRIIMPED TEXTILE PRGDUCTS Alvin L. Breen, Kennett fiquare, Pa, assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Nov. 3, 1953, Ser. No. 771,676 6 (Jlairns. (Cl. 28-82) This invention relates to synthetic textile fibers and particularly improved textile fibers possessing a permanent crimp.

This application is a continuation-in-part of my copending applications Serial Number 412,781, filed February 26, 1954, now Patent No. 2,931,091 issued April 5, 1960, and Serial Number 621,443, filed November 9, 1956, and now abandoned.

Various methods have been proposed and used to produce crimped synthetic filaments. The principles of these crimping methods comprise mechanical treatment of the filaments spun in normal fashion as well as application of specific conditions of spinning or after-treating which bring about dilferential physical properties over the crosssection of the single filaments.

Newer proposals of producing an improved crimp in synthetic fibers comprise the spinning of two or moredifferent materials together so that they form a unitary filament which contains the components in an eccentric relation over the cross-section of the filaments. When, for instance, two materials are used together which possess substantially different physical properties, for example, different residual shrinkage, a crimp is brought about by the application of a suitable after-treatment to the spun and drawn composite filaments. These crimped filaments may be quite satisfactory as long as only relatively small tensions are applied during their use. However, with the application of higher tensions, the crimped filaments of the prior art do not possess the optimum properties and the highest possible crimp retention. Perhaps this is one reason that none of these composite crimped filaments have been commercially produced and used.

Additionally, previously known composite crimped filaments have the disadvantage that part of the crimp is lost or becomes unavailable in fabrics composed of such filaments, due in the large part to the fact that the filaments become compacted and lose freedom of movement in the fabric; this results in the production of fabrics of reduced covering power or leanness.

It is, therefore, an object of the present invention to provide crimped twoor multi-component composite filaments having improved crimp characteristics and improved utility in textile fabrics. It is a further object of the invention to provide filaments in yarns composed of such filaments which exhibit improved covering power when embodied into fabrics. Further objects will appear hereinafter.

The objects of this invention are effected by producing a crimped composite filament of synthetically formed polymers having the capacity of changing the amount of crimp upon being exposed to the elfect of a swelling agent and of reverting to the original crimp upon removal of the swelling agent. This characteristic is, for convenience, referred to as reversible crimp; generally speaking this characteristic of the filaments of this invention is observed by the squirming of the filaments upon both application and removal of the swelling agent. The new improved crimped filaments of this invention may be obtained by different methods. One method comprises spinning together two or more synthetic'polymeric materials, at least one of which is fiber-forming, in such a way that the materials form over the cross-section of the single composite filament two or more distinct zones which extend through the entire length of the filament in eccentric fashion, whereby only one, or, alternatively, part of or all the components form the surface of the single composite filament, stretching the composite filament and subjecting the thus treated composite filament in a substantially tensionless state to a shrinking treatment. (For convenience, the following discussion will refer to two component filaments although the filaments may, if desired, have more than two components.) In accordance with the present invention, one component of the composite, drawn filaments has a substantially greater shrinkability than the other component in order to develop crimp. Furthermore, one component of the crimped filaments of the present invention swells, longitudinally of the filament, to a substantially greater degree than the other component. By virtue of the above noted characteristics, composite filaments of this invention, under the influence of a shrinking agent, develop a crimp which, upon exposure of the filament to a swelling agent, is, at least in part, altered but is regained upon removal of the swelling agent. The value of this crimp reversibility is evidenced by the ability of the filaments in yarns of this invention, when embodied in a fabric, whether or not the filaments are crimped prior to their conversion into a fabric, to move freely in the fabric under the influence of a swelling agent such as water, but, nevertheless, tend .to regain the original crimp in the fabric with removal of the swelling agent, as by drying. Fabrics containing these novel filaments acquire a high degree of fullness or covering power after the fabric treatment and retain this fullness even after being subjected to such treatment repeatedly. It will be understood that fabrics composed of the novel filaments can beneficially also be subjected to a physical Working of the fabric to develop fullness and covering power to the greatest degree.

To develop adequate crimp in the composite filaments, the shrinkability of one component should be at least 1% greater than the shrinkability of the other component, that is, said component has at least 1% greater loss of the original length upon shrinking than the other component. The shrinkability of a component is determined by measuring the shrinkage, upon immersion in boiling water under no tension, of a monocomponent filament made from the component polymer (spun and stretched or drawn under substantially the same conditions as the composite filament). If a component cannot be spun into a monocomponent filament, e.g., because its molecular weight is too low, its shrinkability is determined by extrapolation from a graph of the shrinkage characteristics of monocomponent filaments of the same polymer (in diiferent, spinnable molecular weights).

In order to develop the crimp reversibility characteristic of filaments of this invention, one component of the crimped filamentshould have a longitudinal swellability (i.e. reversible length change by test A) after shrinkage at least 0.05% and preferably at least 0.10% more than that of the other component. Longitudinal swellability of a component is determined by measuring the increase in length of a monocomponent filament of the component polymer (stretched or drawn and shrunk under the same conditions as the composite filament) upon being irnmersed in aqueous medium used for the testing of the swellability of both components. If a component cannot be spun into a monocomponent filament, its swellability is likewise determined by extrapolation from the swellabilities of monocomponent filaments of the same polymer.

For all reversible length changes denoted by test A the tests are executed with strands of approximately denier and approximately 15 inches long as follows. The samples (previously relaxed by a boiloff) are clamped in a tensile tester with a small amount of slack and held in the proper medium (air, cold water, or hot water) for about 2 minutes. The mechanically driven clamp is then started at a low rate of elongation (0.3 inch per minute); it is stopped and reversed immediately when the stress-strain curve starts to depart from the zero line. The true length of the sample is then calculated from the clamp distance in the starting position and the chart distance between the start of the test and the point where the stress-strain curve began.

After wet tests the samples are dried (while clamped) by means of a hair dryer, and the length of dry strand at room temperature determined as above. Wet to dry cycles are repeated until the length change becomes constant. As a rule some shrinkage occurs during the first cycle. For most samples, satisfactory results are obtained with three cycles.

The reversible length change is calculated in percent, based on the final dry length of the sample.

length Wet-length dry final length dry X 100 Results from at least four different strands are averaged to obtain a representative value.

A second test for equilibrium reversible length change whose data is designated by test B was devised which gives results more reproducible than test A above but which in general agrees with those results. In this test strands of the drawn, unrelaxed continuous filaments are boiled in water for 15 minutes. Strands of approximately 300 total denier and 6 inches long are then suspended vertically from a rubber-tooth clamp and weighted with 1.2 gram clamp. The sample is mounted vertically in a stoppered glass tube containing a desiccant in the bottom. The tube is stored vertically overnight (18-24 hours) at 70 C. After the 70 C. conditioning to dry the sample, the 70 C. dry length, i.e., the distance between clamps, is determined with a cathetometer. The desiccant is then removed from the tube, the tube filled with water and stored vertically at 70 C. for 6 hours. It has been determined that all samples reach an equilibrium Wet length at 70 C. in this period. The length of the Wet sample is determined at 70 C. The cycles are repeated as required to obtain reproducible results.

One component of the crimped filament should have a reversible length change by test B after shrinkage of at least 0.4% and preferably at least 0.6% more than the other component in order to develop crimp reversibility.

The crimped fibers of this invention may contain helices which reverse direction at irregular intervals. Accurate measurements of crimp reversibility require samples without these reversals. Preparation of such filament samples was accomplished by pretwisting of the filament prior to application of the crimping medium to the same degree as the crimp frequency found by examination of similar filaments crimped without pretwisting. For crimp reversal measurements, the pretwisted filament was crimped free of tension by immersion in boiling water. The crimped filament was then suspended in a tube and kept from floating or bending by a small weight (1 milligram) attached to the lower (free) end, the weight being pointershaped to permit measuring and counting rotations of the pointer during crimping and uncrimping. The filament was treated successively to cycles each consisting of a 5 minute exposure to 25 C. water followed by a minute drying period in 25 air. The crimp changes, i.e., revolutions of the pointer, were averaged for the 5 cycles and expressed as revolutions per centimeter of extended (straight) dry filament. Values from at least three filaments tested as above were averaged to obtain the crimp reversibility of a fiber. The crimp reversibility values were corrected to a four denier per filament figure which can readily be done since crimp reverisibility is inversely proportional to the cube root or denier.

Crimp reversibility values by the above method are hereafter designated test A.

Reversible length change:

Again it was found that more reproducible crimp reversibility values were obtained under equilibrium conditions (corresponding to the reversible length changes by test B) than by the above test, although the same general results were obtained. Data measured by such an equilibrium test will be designated hereafter as by test B. In this test a single filament is separated from the single end or tow of drawn, unrelaxed fibers. A three-inch length of the filament is attached to opposite sides of a rectangular copper wire frame with slack between the ends. The rack and filament is then boiled off for 15 minutes to develop the crimp. The crimped filament is then transferred to a special viewing holder by taping or gluing the ends so that about 10% slack is present and the filament length between the clamped ends is approximately 2.5 inches The filament and viewing holder is then mounted vertically in a stoppered test tube containing desiccant. The tube is stored vertically overnight (18-24 hours) at C. Following this conditioning period to dry the filament the tube is then brought to room temperature (approximately 25 C.). After allowing 30 minutes for cooling the total number of crimps in the filament between the fixed ends are counted. In counting, any crimp reversal points present are ignored. The desiccant is then removed from the glass tube, the tube filled with water and stored vertically at 70 C. for 6 hours. The number of crimps in the wet fiber are counted as above. The cycles are repeated as required to obtain reproducible results. The equilibrium crimp reversibility or change in crimps/inch of crimped length from 25 C. dry to 70 C. wet expressed as Ac.p.i. is obtained by the following equation where the sign of Ac.p.i. is ignored.

number'of crimps (25 0. dry) nurnber of crimps (70 C. wet) In the spinning, the polymers are not appreciably blended together in the melt but are fed separately to a shaped orifice where they are simultaneously extruded. The orifice is, then, adapted to receive the components separately for simultaneous extrusion to form a filament in which each component is substantially localized but is held to the other component in an eccentric relation. The extrusion can be such that the components are localized and held together in a side-by-side structure in which both components form part of the surface of the composite. The extrusion may also be such that one component forms a core and the other a sheath to form a composite referred to hereinafter as a sheath-core structure. In this structure only the sheath contributes to the surface of the composite. With the spinnerets described herein, melt spinning leads to composites which are generally smooth and have cross-sections which are substantially round with boundary lines that are regular.

The composite filaments are subjected to stretching, and then given a shrinking treatment while substantially free of tension and thus free to shrink.

In the figures:

FIGURE 1 is a plan view of the spinneret assembly shown in FIGURE 2;

FIGURE 2, taken on line 2-2 of FIGURE 1, is a cross-section of a spinneret of this invention showing the routes of polymer in the formation of sheath-core structures;

FIGURE 3 is taken on line 33 of FIGURE 2;

FIGURE 4 is taken on line 4--4 of FIGURE 2;

FIGURE 5 is an enlarged section of the bottom portion 10 in the vicinity of the orifice of FIGURE 2;

FIGURE 6 is a cross-section of a spinneret of this invention showing the flow of polymer in the formation of side-by-side structures;

FIGURE 7 is taken on line 77 of FIGURE 6;

FIGURE 8 shows cross-sections of the sheath-core fila ments of this invention;

FIGURES 9, l9 and 11 show cross-sections of the different forms of side-by-side filaments of this invention;-

FIGURE 12 is a sectional perspective of a fragment of a composite in a crimp form referred to as alpha crimp;

FIGURE 13 is a sectional perspective of a fragment of a composite in a crimp form referred to as beta crimp; and

FIGURE 14 is a diagram of apparatus which can be used in applying a process of this invention in a continuous manner.

Referring first .to FIGURE 2 it can be seen that the top component or filter pack 1 of the spinnerethas two chambers 2 and 3. Each is fed a different polymer. The chambers are separated by wall 4 and in the bottom of the top portion are a plurality of holes 5 cooperating with outlets below. The chamber 3 and the holes 5 therein cooperate with the grooves or recesses 6 and 23 in the center portion or adapter 7 and feed the polymer melt to the vertical holes 8,0r tubes 31. These tubes 31 extend downwardly into the orifices 9 contained in the bottom portion or spinneret face 10. The chamber 2 permits the feeding of polymer downwardly through holes 5 which cooperate with holes 11 in centerpor-tion 7 to permit the flow of polymer to grooves or recesses 12 and 2,9 in the bottom portion 10. Grooves 12 cooperate with orifices 9 to permit the flow of polymer from hole 11 through the grooves and into the orifices. The plan views of the top, center and bottom portions may be seen in FIGURES l, 3 and 4, respectively. As shown, gaskets 25 are provided for sealing purposes, the assembly being held together by means of bolts or by pressure.

As shown in FIGURE 2 and in an enlarged manner in FIGURE 5, polymer 13 coming to the holes 3 or tubes 31 from the chamber 3 constitutes the core feed. As this polymer leaves tube 31 which is surrounded by the melt 14 of polymer coming from chamber 2 and constituting the sheath, bonding occurs so that in the tapered section 30 of orifice 9, polymers 13 and 14 are being extruded simultaneously with polymer 14 completely surrounding the polymer 13. It is to be noted that tube 31 is eccentrically located in the orifice 9. This is done purposely to get the eccentric relation of the polymers, for the more pronounced the eccentricity, the better are the crimp results. As can be seen in FIGURE 8, the filaments thus produced by melt spinning have substantially round, smooth surfaces. Even the core is substantially round and smooth and in all cases the core does not break through the surface. That is, even in such a filament as 15 there is polymer 14 surrounding the core even though the core comes very close to the outer edge at one place.

If material 14 has a higher shrinkage than material 13, the crimped structure shown in FIGURE 12 wherein the material 14 is located on the inside of the helical coil is obtained, This type of crimp in which the material 14- having the lower recovery properties is located on the inside of the coil is referred to herein as alpha crimp. Since the material on the inside of the helical coil is the load-bearing constituent of the composite, it is preferred to have that material be the material having the better recovery properties. By the process of this invention, it is possible to produce such crimped filaments as are shown in FIGURE 13. In this figure, material 13 is on the inside of the helical coil and has the better recovery properties. This type of crimp shown in FIG- URE 13 is referred to herein as beta crimp.

A relatively low tension applied to the crimped filament results in extension of the coils and finally in straightening of the coils because of the very low crimp modulus. Tensions which are higher than the crimp modulus will extend the straightened composite filament whereby the shorter component which forms the inside of the coil bears a relatively greater part of the total load applied. It follows therefrom that a relatively higher strain is applied to the load-bearing component than to the coacting component in a tensioned crimped composite filament. When the load-hearing component has the lower recovery properties, which is the case with 7 scissae; lm r and c are as above in the combinations of synthetic high polymers proposed herebefore for the preparation of crimped composite filaments, the degree and tightness of the crimp will be reduced after application of relatively hi h loads, because the load-bearing component does not recover as much as its counterpart. The new preferred composite crimped filaments of this invention do not have this disadvantage because the material with the better recovery properties has been made to be the load-bearing component.

It is evident from the foregoing that it is of great importance for evaluating crimped composite filaments to have a reliable method for measuring the crimp retention. A commonly used method is described e.g. in US. 2,287,099. In this test, relatively low loads, equivaient to 0.03 g./denier are applied to the crimped filaments while immersing them for 30 seconds into water of C. These tensions are much lower than the strain usually imposed on the single filaments in normal use of textile products containing these filaments. Therefore, a more stringent test has been developed, which simulates more the actual conditions encountered in practical use of the crimped filaments.

The crimped yarn or filaments are formed into a skein the length of which is measured without applying any tension ((1, in centimeters). The skein is then loaded with a weight corresponding to 0.01 g./denier and the straightened length of the skein is measured (b, in centimeters). The skein is then loaded for 30 seconds with a weight corresponding to 1.0 g./denier. The filaments are allowed to recover, after removal of the load, for 30 seconds and the length of the skein is again measured (0, in centimeters).

The crimp permanence is calculated by the following equation:

Percent crimp permanence= 100 a The expression relative viscosity (er) as used herein signifies the ratio of the How time in a viscosimeter of a polymer solution containing 8.2% 10.2% by weight of polymer in a solvent, relative to the flow time of the solvent by itself. Measurements of relative viscosities given in the examples were made with the following solutions: 5.5 g. of a polyamide in 50 ml. of 90% formic acid at 25 C. or 2.15 g. of the polyester in 20 ml. of a 7/10 mixture of trichlorophenol/phenol at 25 C.

The expression inherent viscosity as used in the examples is defined as:

lfl'qr wherein c is the concentration in grams of the polymer in 100 ml. of the solvent and 777" is the symbol for relative viscosity and In is the logarithm to the base 2. The viscosity measurements for calculating the inherent viscosity are made on /2% solutions by weight at 25 C. Meta-cresol and a 7/10 mixture of trichlorophenol/phe- 1101 are used as the solvents for polyamides and polyesters respectively in this determination.

The expression intrinsic viscosity as used herein signifies the value of 1m r at the ordinate axis intercept (i.e., when 0:0) of a line of inherent viscosity values in a graph of lrmr as ordinates with 0 values as ahthe formula for inherent viscosity.

The following examples are illustrative rather than limitative, and parts, proportions and percentages re ferred to in the examples as Well as throughout the specification are by weight unless otherwise indicated.

EXAMPLE I A copolyamide, namely, poly(hexamethylene adipamide/terephthalamide) 70/30 by weight with a relative viscosity of 11 was made by melt polymerization of the salts of adipic and terephthalic acid with hexamethylene diamine. Poly(hexamethylene adipamide) of relative viscosity 41 was spun with the above-mentioned copolyamide as sheath and core, respectively, eccentrically to each other by an apparatus operated similarly to that shown in the drawings herein but specifically described in my copending patent application Serial No. 614,640 filed October 8, 1956, now Patent No. 2,987,797 issued June 13, 1961. The pump speeds were adjusted to give a sheath/core ratio by volume 55/45, the two polymers being cospun at 290 C. into air at 25 C., and the resulting yarn wound up at 800 y.p.m. (yards per minute). The wound yarn had a core of kidney-shaped cross section as illustrated in my said last mentioned copending application, being thus eccentric to the sheath. The yarn was drawn 290% (3.9 times the original length) over a hot draw pin at 83 C. and thence in contact with a hot plate at 160 C. and collected on a bobbin. The yarn developed an excellent crimp in 95 water. The crimped yarn had a crimp reversibility by test A of 0.09 and had an initial modulus (M in 25 water of about 15. Model monocomponent filaments of the copolyamide and the polyamide had swellability (i.e. reversible length change by test A) of 2.61% and 3.13%, respectively, and had shrinkages of 5% and 8.3%, respectively. The differential equilibrium reversible length changes of the copolyamide and the polyamide by test B was 0.41. The equilibrium crimp reversibility by test B of the crimped composite fiber was 0.90 change in crimps/inch of crimped length.

EXAMPLE II Poly(ethylene terephthalate) flakes having an intrinsic viscosity of 0.67 in a solvent mixture of 58.8 parts by weight phenol and 41.2% by weight of trichlorophenol and poly(hexamethylene adipamide) flakes having an intrinsic viscosity of 1.02 in m-cresol are melted separately and extruded at 285 C. through a multi-hole spinneret assembly shown in FIGURE 2. The extruded filament is air quenched. The polyester melt is extruded through the inner tube of the spinneret and the polyamide through the outer space surrounding the tubes, thus forming a sheath-core filament. FIGURE 8 shows a cross-section of a bundle of the eccentric sheath-core filaments thus obtained. This drawing, based on a microphotograph, shows clearly the eccentric position of the polyester cores in the polyamide sheaths over the cross-section of the single filaments forming the fiber bundle.

The eccentric sheath-core filaments are attenuated by pulling them as they are spun away from the spinneret holes with a speed which is about 100 times as high as the speed of the extruded melt. After spinning and cooling, they are drawn over a pin at room temperature C.) to 3.3 times their original length. About 100 yards of the stretched filaments were tightly wound on a bobbin, and the bobbin was heated for minutes in an electric oven, the temperature of which was 115 C. The cooled filaments were then unwound from the bobbin and showed upon inspection no distinct crimp. However, they possess a potential crimp which can be developed immediately after the heat treatment or at any time after the fiber is processed into woven textile materials or into knitted goods or after cutting the fibers into staple lengths.

EXAMPLE 1H A part of the continuous filament of Example H containing the potential crimp was skeined and hung in boiling water for one minute without applying any tension to the filaments. A very tight helical crimp developed instantly. The filaments contained on an average 50 crimps per inch. Microscopic inspection of the filaments showed that the core of poly(ethylene terephthalate) was positioned in the outer portion of the single coil and the thicker parts of the polyamide skin were situated on the 8 inside of the single coil. Therefore, the filaments contained the beta crimp.

As determined from model monocomponent filaments, the polyamide sheath and the polyester core had swellabilities, respectively, of 3.13% and 0.08% and shrinkabilities, respectively, of 8.3% and 4.5% (swellabilities i.e., reversible length change by test A). The equilibrium reversible length change by test B of the polyamide and the polyester were respectively 2.70 and 0.0. The crimp reversibility of these filaments was at least as good as those of the crimped filaments of Example 1.

EXAMPLE IV Part of the eccentric sheath-core composite filament yarn of Example II was plied and twisted to a yarn containing 56 filaments with a total denier of 180. The twist was 0.5 turn per inch. This yar-n was knit into tubing which when flattened to double thickness measured 3 /8" wide. A piece of this tubing 12 inches long was placed in boiling water containing 0.5% Duponol for 30 seconds. The fabric was then rinsed, centrifuged and dried in the open air. The dry fabric was found to measure 3%" wide and 5%" long. The bulk and covering power of the fabric were correspondingly increased. Moderate tension cause-d stretching of the fabric beyond the original dimensions but the shrunken form returned almost completely upon release of such tensions. This good shape retention of the boiled-01f knit fabric is attributed to the good crimp retention of the crimped fibers composing the fabric.

If the spun and drawn filaments of Example II are given the shrinkage treatment of Example III without applying first the length stabilization treatment of Example II, highly crimped filaments are obtained. However, microscopic inspection of the cross-section of these crimped filaments shows that the cores consisting of the polyester are positioned on the inner portion of the coils and the thicker portions of the polyamide skin are on the outside of the coils. These fibers therefore possess the alpha crimp and do not possess the crimp retention of the beta type of this invention.

In the foregoing examples the filaments were spun through spinnerets which were found to be especially suited and economical to be used for obtaining a random eccentric sheath-core structure in the single filaments. However, the invention is not limited to the application of these specific spinnerets. Any other form of a spinneret which permits production of a composite filament which contains at least two components in an eccentric relationship over the full length of the filament can be used. There are no restrict-ions with respect to which component forms the core and which component forms the sheath in the sheath-core structures of this invention. Though it is generally preferred to choose the component with the higher recovery properties to form the sheath, other considerations like solubility, spinning technique, appearance and hand, and physical properties may make the reverse order desirable. The invention is further not limited to the eccentric sheath-core filaments. Any other form of a composite filament which contains the components in an eccentric relationship over the cross-section of the single filament may be utilized instead of the sheath-core structure shown in the examples. So for instance, the components can also be spun in the socalled side-by-side relationship wherein the components are combined at only part of their surface and both components take part of the surface of the composite filament. However, the sheath-core structures are preferred in this invention because the problem of coherence, which exists with many polymer combinations, particularly on drawing the side-by-side structures, is practically eliminated in sheath-core structures. The latter structures therefore permit a much wider application of this principle. Other embodiments include composite filaments which are composed of more than two components. Filaments have been produced in the above examples which consist of about equal parts of the two components. However, sometimes it might be preferred to use a relatively higher amount of one component and a correspondingly lower amount of the other component. Good results can usually be obtained with compositions of at least by weight of one component and 80% by weight of the counterpart up to a ratio of 50% by weight of both components. Those composite filaments containing about equal portions of both components are preferred because of the higher tightness and permanence of the crimp achieved.

Sometimes it might be desirable to spin a bundle of filaments which comprises composite filaments containing the components in various ratios through one and the same spinneret. An example is a bundle of two-component composite filaments which comprises filaments consisting of 20% by weight of the load-bearing component and 80% by weight of the other, a %/70% ratio, a 40%/ 60% ratio and a 50%/50% ratio, respectively. Such filament bundles containing composite filaments with various ratios of components can very conveniently by produced by utilizing the spinneret which is shown in FIGURES 6 and 7. The spinneret shown is composed of two parts. In the upper portion 16 are two chambers 17 and 18 cooperating with holes 19 in the bottom plate of the top portion. These holes permit the feeding of polymer to grooves or recesses 20 in the bottom portion 21 of the spinneret. The polymer coming from hole 19 goes into the recess 22. immediately below it and is fed to a plurality of recesses 20. Each recess contains and cooperates with a spinneret hole 24. In each spinneret, provision is made for a gasket 25 and conventional means, as by bolting or pressure, can be used to hold the various spinneret elements in place during operation.

However, in the sipnneret shown by FIGURES 6 and 7 there is no tube located in the spinneret orifices 24 such as are in the spinneret orifices 9. Thus, in this modification polymer coming from chamber '17 and the other polymer coming from chamber 18 meet at the orifices 24 and are extruded simultaneously to form sideby-side structures. Cross-sections of such structures are shown in FIGURE 9, these structures being designated by reference number 26, the parts being 27 and 28.

The spinning, drawing, and length stabilization of the load-bearing component in the composite filament and the after-treatment for bringing about the crimp were described in the foregoing as a discontinuous procedure wherein each treatment was carried out as a separate processing step. The same outstanding results, however, can be achieved in a fully continuous process. An apparatus especially useful for the continuous procedure is shown in the schematic drawing of FIGURE 14.

The apparatus comprises a draw pin 32 at which the stretching occurs, a heating medium 33 such as a hot metallic surface, and a draw roll 34. The following Example V is representative of a continuous process for producing the composite filaments.

EXAMPLE V Following the procedure described in Example II, composite sheath-core poly(ethylene -terephthalate)-poly (hexamethylene ad-ipamide) filaments are extruded through a spinneret like that shown in FIGURE 2 having 34 holes. The filaments 35 are attenuated .by drawing them from the spinneret at approximately 500 times the speed with which the polymer leaves the spinneret holes. The bundle of filaments is, after cooling, continually drawn over a draw pin 32 which is heated to 85 C. On its path to the draw roll the filament bundle is led over a hot plate 33 which is heated to 140 C. The total draw imposed on the yarn is 3.56. The filaments, the thickness of which corresponds to approximately 2 deniers, are substantially uncrimped but they possess the potential crimp. Subsequent tension-less treatment in boiling water by short immersion developed readily a tight helical crimp. The crimped filaments have on an average approximately 60 crimps per inch and a crimp elongation of 170% and a crimp retention of when measured according to the above-described test with the application of a load of l g./denier for 30 seconds.

icroscopic inspection of the crimped filaments showed that the filaments have the beta-type crimp wherein the thicker portions of the polyamide skin form the inside of the single coils.

Similar composite filaments produced according to the foregoing method, however, omitting the length stabilization on the hot plate had a crimp elongation of only 70% and a crimp retention of only 40% when measured by the test used above.

Length stabilization by the hot plate or equivalent hot treatment reduces the shrinkage of the polyester from 11.5% to 4.5% and reduces the shrinkage" of the polyamide from 10.5% to 8.3%.

The filaments of the above example with the beta-type crimp had a crimp reversibility by test A of 0.48. Monocomponent filaments corresponding to the components in the beta-type crimp filaments had swellabilities (i.e., re versible length change by test A) of 3.13 and 0.08%, respectively, for the polyamide and the polyester. The reversible length change by test B for the polyamide and the polyester were 2.70 and 0.0 respectively. The composite filament had an equilibrium crimp reversibility by test B of 8.1 changes in crimps/inch of crimped length.

EXAMPLE VI The following example is directed to a dry spinning process in which the composite filament is spun from different polymers of acrylonitrile as the components of the filament.

Copolymer (a) with an intrinsic viscosity of 1.5 as measured in dimethylformamide was made from acrylonitrile, methyl acrylate, and sodium styrene-sulfonate using the technique of US. Patent 2,628,223, in which the monomers were fed to the reactor at relative rates of 93.63, 6.00, and 0.37, respectively.

Copolymer (b) with an intrinsic viscosity of 1.5 was made in a similar manner from acrylonitrile and sodium styrenesulfonate with relative feed rates of the monomer of 97.0 and 3.0, respectively.

Copolymer (c) with an intrinsic viscosity of 2.1 was made in a similar manner from the continuous polymerization of a feed consisting of 94 acrylonitrile and 6% methyl acrylate.

(A) A 25% solution of copolymer (a) in dimethylformamide and a 25% solution of copolymer (b) in dimethylformamide were spun as the two components of a side-by-side filament with a spinneret similar to that shown in FIGURES 6 and 7 modified so as to extrude equal volumes of each component in each filament. The solutions were extruded at C. into an inert gas at C. and wound up at 200 y.p.m. Typical cross-sections of the yarns produced by this example are shown in FIG- URES 10 and 11 as separate components of the filaments (indicated by the shading). FIGURE 10 shows one filament among those spun as having the components more or less length-wise of the cross-section, whereas FIGURE 11 shows the components as approximately divided midway of the length of the cross-section. The filaments occur among other filaments spun in the same group at the same time, and the relationship of the components will vary from those shown in FIGURE 11 while still retaining the side-by-side relationship of the components. (The spun yarn was drawn 300% (4x) in 95 C. water and dried.) Single component filaments of each component polymer spun and drawn in the same manner as above had swellabilities (test A) of 0.46 and 0.64%, respectively, after shrinking. Equilibrium reversible length changes by test B of 3.7 and 6.5% respectively were observed.

(B) Composite filaments were spun from polyacrylonitn'le (the homopolymer) with an intrinsic viscosity of 1.5 and copolymer (c) with an intrinsic viscosity of 1.5 as in example (A) above, and the spun yarn was drawn 11 300% (4X the original length) in steam. Single component filaments of the component polymers, spun and drawn in the same manner, had swellabilities (test A) of 0.19 and 0.16%, respectively, after shrinking. Equilibrium reversible length changes by test B of 1.0 to 1.3% were measured.

Samples of both composite yarns (A) and (B) developed a helical crimp of approximately 20 crimps per inch of extended fiber length (i.e., with the crimps pulled out). The crimped filaments had crimp reversibility (test A) of 0.11 and 0.0 respectively for samples (A) and B). Equilibrium crimp reversibilities by test B of 4.5 and 0.40 were obtained. The value of the wet modulus at 25 C. is directly related to the work that the crimped fiber can do in the crimp reversing step between the wet condition and the dry condition. For filaments that have a dog-bone cross-section, as shown in FIGURES and 11, the effective modulus that is related to the squirming of the fiber is considered to be 60% of the measured value. The effective modulus values (25 C. wet) were 13 and 28 for samples (A) and (B), respectively.

Tufted fabrics of similar construction were made from the 3-denier per filament unrelaxed (uncrimped) filaments of (A), (B), and homofilaments of copolymer (a). The fabrics were boiled in water for 30 minutes, air-dried, and brushed up with a hand card. Each pile was then crushed down to 10 to 20% of its initial height by a 1 kilogram weight 2 inches in diameter for 24 hours. After the weight was removed, the fabric was allowed to stand in room air for 24 hours. The fabric was then immersed in 60 C. water for 1 minute without agitation and airdried. The fabric from single component yarn showed no recovery after any of the treatments. The fabric from the filaments of (A) (having reversible crimp) recovered about 90% of its height after 24 hours and recovered 100% after the wetting and drying cycle. The fabric from the filaments of (B) (no reversible crimp) showed no dry recovery and only about 30% recovery after wetting and drying.

Staple fiber (70 parts) was out from the filaments of example (A) and blended with wool (30 parts), yarns spun, and a Shetland-type fabric made and subjected to the usual finishing and fulling operations employed for wool fabrics of this type. The finished fabric was equivalent to a similar all-wool fabric in bulk and cover, low shrinkage obtained in the fabric finishing steps (e.g. 35 and shrinkage in the warp and fill directions, respectively), elasticity and liveliness, and soft, pleasing surface handle. Similarly constructed fabrics of synthetic filaments not having reversible crimp displayed poor bulk and cover despite the high shrinkages observed, poor elastic properties, and had harsh surface handle.

Crimped fibers were cut in 2-inch lengths, hand carded (2) placed in 25 C. water for 40 minutes to recover. The heights of the recovered pellets after treatments 1 and 2 were then measured. Results with the composite filaments in Examples VI-A, VI-B, and the homocomponent filaments of copolymer (0) are given in the next table as items A, B, and C, respectively.

[Pellet height, in inches] Item Com- Recovered Recovered (3) (2) pressed Dry 4 Cold-Wet hours 40 minutes The ability of the crimped fibers having a reversible crimp to recover from a deformation in the presence of an aqueous medium is plainly seen from the above results.

EXAMPLE VII The monomers acrylonitrile (AN), sodium styrene sulfonate (SSA), methyl acrylate (MA), methacrylic acid (MAA) and acrylamide (AC) were used to make polymers and copolymers using monomer feed ratios as shown in Table I below. Composite filaments were made and crimped as in Example VI. Monocomponent filaments were made in a similar manner from the polymer components of the composite yarns. Items A, B and C of Table I were made of polymers with an intrinsic viscosity of 2.0 (dimethyl formamide) and the yarns were drawn 700% (8X original length) in steam to yield filaments having effective 25 C. wet modulus values of 21, 16 and 18 respectively and deniers per filament of 6, 2 and 3 respectively. Item D of Table I was drawn 300% (4X original length) in 95 C. water.

The as-spun yarn of item E was washed free of residual solvent and then cross-linked by treatment with formaldehyde and 2% hydrochloric acid. The cross-linked yarn was then drawn 300% in a 0.5% aqueous solution of sodium bicarbonate at 95 C. The drawn yarn was wound on a package and boiled in a 0.5 aqueous solution of sodium bicarbonate in a taut condition for thirty minutes and then dried. A portion of the yarn was boiled free of tension for thirty minutes in water to develop crimp (designated salt in Table I below). Another portion of the yarn was boiled free of tension in 1% hydrochloric acid for thirty minutes followed by boiling in water (designated acid in Table I) I The pertinent data and physical properties for this Example VII are stipulated in the following Table I.

Table 1 Uomofilament Data Swellability, Composite Filament Percent Item Component I-Monomer Feed Coniponent IIMonomer 1 eed Test A Crimp Reversibility Crimps Test 13, Per

I-II Extended I II I II Test A Test B Inch 0. 71 0.10 0. 52 4. 3 0. 73 13.2 30 0. 50 0. 27 0. 29 1. S 0. l7 8. 2 25 AN/SSA, 97.5/2.5 AN/SSA, 98.5/1 0. 38 0. 25 0. 12 0. 0. 09 2. 0 10 D AN/hIA/SSA, 93.6316. AN/MAA, 95/5 0. 40 0. 99 0. 53 3. O 0. 5 4. 4 20 E AN/MAA/AC/SSA, ere 5 3 0.4 AN/HA/SSAJ9163 6/0.37 fj 12. 5

\ (n)=l.5, all others (n)=2.0.

and made into pellets weighing 0.30 gram. The pellets were placed into a cylinder (0.5 inch diameter hole) under a freely sliding piston that exerted 1,000 p.s.i. for two minutes. The height of the pellet under compression was measured. Different compressed pellets of the same Examination of monoccmponent filaments of acrylonitrile copolymers showed that the presence of such monomers in the amount of 2 to 10% or more in the copolymers as: itaconic acid, fumaric acid, sodium methallyl sulfonate, ethylene sulfonic acid and methyl vinyl pyrifiber were: (1) allowed to recover in dry air 4 hours or dine and acrylic acid in addition to those already discussed cause sulficiently high swellability to enable that polymer to be used as the higher longitudinal swelling component of a composite filament.

The effect of the acidic or basic groups discussed above are enhanced by the presence (145%) in the same polymeric component of a neutral monomer. Such neutral monomers when incorporated into an acrylonitrile polymer increase the dyeability of fibers made therefrom with a disperse dye, such as the blue dye prototype 62. Methyl acrylate, N-vinyl pyrrolidone, acrylamide, vinyl acetate and similar monomers are suitable.

The description of the invention has been largely concerned with the making of filaments having only two components with the differences in shrinkability, swellability, etc. referred to herein. It will be understood, however, that the filaments may, in fact, be composed of more than two components provided that two of the components have the characteristics and properties possessed by components in a two-component system.

The filaments of the above examples, and yarns produced therefrom, possess, in common with all the filaments of this invention, the characteristic of crimp reversi bility, that is, the ability to return to the original crimp state spontaneously after having been treated with the swelling agent and after removal of the swelling agent following such treatment. The preferred system exhibiting this characteristic of crimp reversibility involves filamerits which have been crimped by a suitable shrinking treatment and which, upon being swollen, lose a portion of the crimp. Such filaments may be woven or knitted, either in the potentially crimpable or in the crimped state, as continuous filaments or as staple fibers, and if woven in the uncrimped or potentially crimpable state, the crimp may be developed in the fabric by treatment with a suitable shrinking agent. The crimped filaments of the fabric will, upon treat-merit with a swelling agent, as by aqueous treatment in the washing, scouring, dyeing, and other treatments normally applied to fabrics, move around or squirm during such treatments with considerable freedom and, upon removal of the swelling agent, regain the lost crimp with the imparting of a fullness and highly increased covering power to the fabric. Not only is this of advantage in the type of fabric used for clothing, but it is of great importance in piled fabrics such as those used in carpets and upholstery, where the compacting of the fibers under compression incident to use, may be overcome by treatment with water or other swelling agent to cause the fibers to squirm or work out of the compressed state, but, upon drying, the fibers will again revert to their highly crimped and voluminous state prior to their having been compressed. Although the invention has, in its pre ferred form, been applied to filaments which lose at least a part of their crimp upon the swelling treatment, it is within the scope of this invention to utilize a reversible crimp wherein the crimped filaments actually gain additional crimp upon treatment with a swelling agent; in this case, also, the filaments squirm and work around with respect to each other upon treatment with a swelling agent and also upon removal of the swelling agent as by drying, thereby, because of the freedom of movement of the filaments even with increased crimp, insuring the imparting of increased fullness, bulk and covering power to the fabric. Filaments having the property of increasing crimp upon treatment with a swelling agent may be selected from polymers exhibiting this characteristic, particularly where the original crimp was incompletely developed in the init'al crimping treatment and may be further developed by treatment with water, for example, under different conditions of temperature and time of treatment.

Although the invention comprehends filaments having either the alpha or beta type of crimp, the advantages of the beta type of crimp are apparent from the above discussion, and filaments with the beta type crimp represent a preferred form of the invention.

Either component of the composite, crimp reversible 1d filaments of this invention can be found in many groups of synthetic polymer materials. The term synthetic polymer materials signifies polymers which are prepared synthetically from monomeric materials, either as homopolymers or as copolymers. At least one of the components in the composite filaments of this invention will be a fiber-forming component; both components can be fiberforming depending on the physical characteristics desired of the ultimate product, but, as pointed out above, particularly in the case of very low viscosity polymers, one corn ponent may be a non-fiber-forming polymer provided that another component is a fiber-forming polymer. Fiberforming polymers are those which conform to the generally accepted standards for the commercial spinning and drawing of filaments and yarns.

In the above examples various types of polymers, particularly synthetic linear polymers, inclusive of both addition and condensation polymers, have been illustrated, and the polymers may be those spun either according to melt spinning processes or dry spinning processes or by other types of spinning processes. Because of their commercial availability, ease of processing, and excellent properties, polyamides, polyesters, and acrylonitrile polymers are found to be particularly desirable in the practice of the invention. Suitable polyamides and polyesters are described in US. Patents 2,071,250, 2,071,253, 2,130,523, 2,465,319, 2,130,948, 2,190,770, and various other patents. Specific pol-yamides which can be used are poly- (hexarnethylene adipamide), poly(hexamethylene sebacamide), poly(cpsilon-caproamide), and their copolymers. Among the polyesters which maybe used are poly(ethylene terephthalate), particularly useful where heat stabilization is desired, and other polyesters and their copolymers containing dibasic acids, such as sebacic or adipic F acid combined, in recurring units, with glycols having 2 or more carbon atoms in the chain. Other polymers are acrylonitrile polymers, particularly the homopolymer and copolyrners of acrylonitrile containing not more than 20% of the material copolymerizable with the acrylonitrile, polyurethanes, polyureas, polyethylene, polyvinyl chloride, polyvinylidene chloride, and other polymers as well copolymers of these materials with other monomers.

Particularly effective for use as high longitudinal swelling components of the composite filaments are polymers containing combined therein ionizable groups as modifying elements, for example, in polyesters, and acrylonitrile polymers (particularly copolymers); the ionizable groups may be basic or acidic, preferably the latter. The examples illustrate the modification of polymer components by the inclusion, during polymerization, of styrene sulfonic acid, methacrylic acid, itaconic acid, furnaric acid, methallyl sulfonic acid, and similar modifiers containing ionizable groups. The selection of the components to be incorporated into the composite fibers will depend on the physical properties desired of the filaments and yarns, e.g. the optimum residual shrink-age, tensile recovery, elongation, such as is desired for textile filaments, and the like, that is, properties being readily determined by known methods. The physical properties of the desired components, taken alone, can be relied upon for the selection of the components to be used in any given combination. In view of the fact that the composite filaments of this invention are normally subjected to aqueous treatment, it is preferred that the wet modulus at 25 C. of both components be at least 10. A select-ion of high swelling differences together with high wet modulus for both components contributes greatly to the impclling force responsible for the high crimp reversibility characteristic of the filaments of the invention. The product of the difference of swellabili ty (i.e., reversible length by test A) between the components multiplied by the 25 C. wet effective modulus of the composite filament (which can be approximately calculated from the average wet modulus of the components) is preferably at least 1.5.

EXAMPLE VII I A 20% solution in dimethylformamide (DMF) of polyacrylonitrile of (n) 1.95 and containing 27 milliequivalents of acid groups per kilogram of polymer (as determined by titnation in a DMF solution) was simultaneously spun with a 27% solution in DMF of a copolymer of acrylonitrile and styrene sulfonic acid 96/4% by weight composition of (n) 1.54 and analyzing 240 milliequivalents of acid per kilogram of polymer as side-by-side components of composite filaments. The spinneret contained 140 orifices of 0.069 inch in diameter located on a 5.27 inch diameter circle. A mixture of carbon dioxide and nitrogen gases were circulated through the cell at a rate of 57 lbs. per hour. Temperatures of 105, 315, and 180 C. were used for the spinning solutions, head and cell respectively. The thread-line consisting of 140 composite filaments was wound up at 200 y.p.m.

Three hundred fifty ends of yarn produced as above with a combined denier of 382,000 were combined into a tow and drawn to 4 times their original length (i.e., 4X draw ratio) in baths of water at 95 C. which extracted the residual DM'F. The drawn and unrelaxed wet tow was mechanically crimped in a stutter box similar to that shown in Hit-t US. 2,747,233 issued May 29, 1956 to an extent of 6-7 herringbone crimps per extended inch using a stuifer box temperature of 50 C. The crimped tow was then cut into 3%" length staple. The cut staple, loosely arranged in a tray, was dried for minutes in a circulating air oven at 270-275 F. The dried staple had a weak mechanical crimp of 6 to 7 crimps per inch plus 6 to 8 helical crimps per inch.

The above prepared staple develops 16 helical crimps per inch of extended length when boiled free of restraint in water. The helically crimped fibers thus prepared have a Ac.p.i. of 6.4 crimps per inch. The staple has a tenacity of 2.2 grams per denier (g.p.d.), an elongation at the break of 40%, and a denier per filament of 3 after boiling and drying.

Pilling is a well known phenomenon of fabrics made from staple fiber yarns, and can be described as the tendency to form small clusters, clumps, or balls of interentangled fiber ends on the surface of a fabric. Pi-lling propensity can be measured by actual wear-tests or by laboratory tests. The test described in the article Random Tumble Pilling Tester (RTPT) by E. M. Baird et al. in Textile Research Journal 26, 731-735 (1956) is used herein. The pilling ratings have the following means: (1) no pilling; (5) extremely high pilling, (unacceptable) and (9) saturation pilling with intermediate ratings being used.

Similar woolen system yarns were spun from the staple fiber of this example (item 1) and from staple cut from the homo-cut component filaments of copolymer (c) of Example VI (item 2). Similar fabrics were knitted from these yarns and the samples submitted to the pilling tests for various times. Results are given below.

Boiling the fabrics after pilling instead of hand washing reduced the level of the pill ratings on item 1 one more unit than indicated above. Boiling had no efiect on pilling of item 2. This clearly indicates the value of the reversible crimp in reducing the pills on fabrics made of fibers of this invention.

Garments of fleece-type fabrics produced from the fiber of this example and homocomponent filaments of the copolymer (0) of Example VI displayed glazing on the seams after conventional seam pressing conditions. Subsequent steaming on a Hoffman press removed the glaze on fabrics made from fibers of this example but did not afiect the control item.

EXAMPLE IX A series of copolyesters containing sulfonic acid side groups were made by copolymerizing sodium 3,5-di(carbomethoxy) benzene sulfonate (DCBS) with dimethyl terephthalate and ethylene glycol by ester exchange. These copolyesters were melt spun as the sheath of a composite filament around eccentrically disposed cores of poly(ethylene terephthalate) containing meq. of carboxyl groups per kg. of polymer with a relative viscosity of 24.6 using a spinneret similar to that shown in copending and coassigned application Serial No. 519,031 filed June 30, 1955, now US. Patent No. 2,936,- 482, granted May 17, 1960 to l. Kilian. All yarns (34 filaments) were drawn over a hot pin at about 104 C. Physical properties were determined on dry yarns after boiling water for minutes in a relaxed condition. The

. results are shown in Table II.

The above polymers can also be spun into side-by-side types of composite filaments.

Tubing knitted from the above yarns showed a considerable increase in bulking and covering power over control tubing from the polyester homofilaments. Ribbons made with the sheath-core yarns as filling exhibited a much softer hand after boil-ofi than did those with all homofilamcnt yarns.

The effect of the acidic group in a component can be enhanced by the incorporation of a neutral modifier in the polymer as by replacing a portion of the ethylene glycol with a polyethylene oxide glycol of molecular weight 6000 in the polymerization.

Table II Sheath Component Orimps/ Sheath/ Draw Inch of Item Core Denier Ratio Crimped ACPI Mol. Acidity Weight Length percent meqJ DCBS kg.

Composite filaments prepared for use in accordance with the present invention are subjected to a drawing (permanent stretching) operation in order to develop the ability to crimp. The conditions applied to drawing the spun multicomponent filaments may vary in wide limits. The drawing characteristics of the components can readily be determined from those of monocomponent filaments of each of the component polymers of the composite filaments. The drawing can be accomplished in accordance with known principles applicable to the particular polymers of the composite filaments and, in general, the composite filaments are drawn at least of original undrawn length) and preferably about 2-8 times the original lengths. Prior to drawing the filaments are attentuated; that is, they are slenden'zed by pulling the freshly extruded filaments away from the orifice at a rate faster than the extrusion rate. The drawing or orientation step is in addition to attenuation, but also has a slenderizing effect. The extent of drawing will, of course, also depend somewhat upon the nature of the particular polymers used in the composite filament and upon the type of eccentric relationship between those polymers in the composite filament.

In considering the extent of drawing, one should take I into consideration the amount of draw which may be at- 1? tected during the spinning of the filaments, and, in fact, the desired amount of drawing may be alfected during spinning rather than as a separate drawing step following the windup of the filaments from the spinning operation.

The shrinkage of the composite filaments in order to effect crimping, may be carried out by the use of any suitable known shrinking agent. Shrinking will ordinarly be carried out by the use of hot aqueous media such as hot or boiling water, steam, or hot highly humid atmosphere, or by the use of hot air or other hot gaseous or liquid media inert to the polymers of the composite filaments. The shrinking temperature is generally in the neighborhood of 100 C. but may be higher or lower, e.g., 50 C. up to about 150 C. or even up to a temperature not exceeding the melting point of the lowest melting polymeric component of the fiber.

The filaments of the present invention can be fabricated into knitted or woven goods, either as continuous filament or as yarns composed of cut staple fibers. The new continuous or staple filaments of this invention can be crimped before they are further processed or in any state of processing, for instance, after they are spun into yarns or after the woven or knitted goods are made from these yarns. Another important application comprises the processing of the continuous filaments into bulky fabrics which again can be carried out with the continuous filaments in the crimped or uncrimped state. In the latter case, the crimp can be developed after weaving or knitting the yarns obtained therefrom or in any stage of the processing. Very interesting applications of the continuous yarns are, for instance, the preparation of worsted fabrics which may be woven from the uncrimped yarns containing the potential crimp and which are crimped after weaving and finishing. These worsted fabrics have an appearance and hand very similar to those obtained from staple yarns. However, they do not possess the disadvantages in processing and use of these fabrics. Another very important application of the fibers of this invention comprises the use in carpets and other heavy textile goods where again the fibers containing the potential crimp can be knitted or woven and the crimp is developed in the finished goods.

Any departure from the above description which conforms to the present invention is also intended to be included within the scope of the claims.

I claim:

1. A composite filament crimpable from a straight state upon relaxation by shrinking comprised of at least two components of synthetic polymeric compositions, each of said components having an initial modulus at 25 C. in water of at least grams per denier, said components being eccentrically disposed toward each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, each of said components extending throughout the length of said filament, one of said components having a shrinkability of at least 1% greater than any of said other components and one of said components having a reversible length change after shrinkage evidenced by an increase in length of at least 0.05% greater than any of said other components when treated with a swelling agent with said component substantially returning to its original length upon removal of said swelling agent, such response providing crimp reversibility in said filament characterized 18 by squirming of said filament upon treatment with and upon removal of said swelling agent after said shrinkage.

2. A composite filament crimpabie from a straight state upon relaxation by shrinking comprised of two components of synthetic polymeric compositions, each of said components having an initial modulus at 25 C. in water of at least 10 grams per denier, said components being eccentrically disposed toward each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, each of said components extending throughout the length of said filament, one of said components having a shrinkability of at least 1% greater than the other component and having a reversible length change after shrinkage evidenced by an increase in length of at least 0.10% greater than the other component when treated with a swelling agent with said component substantially returning to its original length upon removal of said swelling agent, said filament assuming a crimped state upon relaxation by shrinking and exhibiting crimp reversibility characterized by squirming of said filament upon treatment with and upon removal of said swelling agent after said shrinkage, each of said components being present in said filament in amount between about 20% and about 80% by weight of said filament.

3. The filament of claim 2 wherein one component is polyhexamet-hylene adipamide and the other component is a copolymer of by weight hexamethylene adipamide and 30% by weight hexarnethylene terephthalamide.

4. A composite filament crimpable from a straight state upon relaxation by shrinking comprised of at least two components of synthetic polymeric compositions, each of said components having an initial modulus at 25 C. in water of at least 10 grams per denier, said components being eccentrically disposed toward each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, each of said components extending throughout the length of said filament, one of said components having a shrinkability at least 1% greater than any of said other components and having a reversibl length change after shrinkage evidenced by an increase in length of at least 0.10% greater than any of said other components when treated with a swelling agent with said component substantially returning to its original length upon removal of said swelling agent, such response providing crimp reversibility in said filament characterized by squirming of said filament upon treatment with and upon removal of said swelling agent after said shrinkage.

5. A high bulk fabric prepared from the filaments of claim 1.

6. The composite filament of claim 2 wherein said components are present in essentially 50/50 weight ratio.

References Cited in the file of this patent UNITED STATES PATENTS 2,200,134 Schl-ack May 7, 1940 2,209,919 Herrmann July 30, 1940 2,351,090 Alles June 13, 1944 2,439,813 Kulp et al. Apr. 20, 1948 2,439,814 Sisson Apr. 20, 1948 2,439,815 Sisson Apr. 20, 1948 2,571,457 Ladisch Oct. 16, 1951 2,674,025 L-adisch Apr. 6, 1954 FOREIGN PATENTS 514,638 Great Britain Nov. 14, 1939 

1. A COMPOSITE FILAMENT CRIMPABLE FROM A STRAIGHT STATE UPON RELAXATION BY SHRINKING COMPRISED OF AT LEAST TWO COMPONENTS OF SYNETHETIC POLYMERIC COMPOSITIONS, EACH OF SAID COMPONENTS HAVING AN INITIAL MODULUS AT 25*C IN WATER OF AT LEAST 10 GRAMS PER DENIER, SAID COMPONENTS BEING ECCENTRICALLY DISPOSED TOWARD EACH OTHER IN DISTINCT ZONES WITH ADJOINING SURFACES BEING IN INTIMATE ADHERING CONTACT WITH EACH OTHER, EACH OF SAID COMPONENTS EXTENDING THROUGHOUT THE LENGTH OF SAID FILAMENT, ONE OF SAID COMPONENTS HAVING A SHRINKABILITY OF AT LEAST 1% GREATER THAN ANY OF SAID OTHER COMPONENTS AND ONE OF SAID COMPONENTS HAVING A REVERSIBLE LENGTH CHANGE AFTER SHRINKAGE EVIDENCED BY AN INCREASE IN LENGTH OF AT LEAST 0.05% GREATER THAN ANY OF SAID OTHER COMPONENTS WHEN TREATED WITH A SWELLING AGENT WITH SAID COMPONENTS SUBSTANTIALLY RETURNING TO ITS ORIGINAL LENGTH UPON REMOVAL OF SAID SWELLING AGENT, SUCH RESPONSE PROVIDING CRIMP REVERSIBILITY IN SAID FILAMENT CHARACTERIZED BY SQUIRMING OF SAID FILAMENT UPON TREATMENT WITH AND UPON REMOVAL OF SAID SWELLING AGENT SAID SHRINKAGE. 